The present invention relates to a switch device operated to actuate various apparatuses.
A rotary switch is typically rotated to activate, inactivate, or change the control amount of an apparatus. Japanese Laid-Open Patent Publication Nos. 2004-22301, 2004-220957, and 2003-086059 describe conventional rotary switches. A conventional rotary switch includes a click mechanism for ensuring a reliable switching operation or for providing an operator with a tactile sensation. For example, a mechanical click mechanism may have recesses formed on a fixed member of a rotary switch and a projection formed on a rotary member of the switch. A resistance is generated when the projection, which is engaged with one of the recesses, moves to an adjacent one of the recess. The resistance is perceived as a tactile sensation by the person operating the switch.
The rotary switch may be used to operate a device that displays various menu screens (input screens) for function selection, such as a navigation system. The number of items that can be selected on each menu screen usually differs depending on each menu screen. However, the function selection on each menu screen is required to be executable by operating the single rotary switch. Therefore, a variable tactile sensation mechanism (click mechanism) has been proposed. The variable tactile sensation mechanism changes the number of times clicks are generated (number of times the operator receives a resistance) per operation angle unit of the rotary switch for each menu screen.
One example of a variable tactile sensation mechanism is an electric click mechanism. The electric click mechanism includes a motor, which is connected to a switch knob of a rotary switch directly or via a transmission mechanism, for electrically providing the switch knob with a click using the drive force of the motor. When the rotary switch is operated, the electric click mechanism varies the generated resistance by changing the amount of current flowing through the motor. For example, when an input screen is displayed on a car navigation system for selecting buttons or icons, a relatively large resistance is generated for the operation of the rotary switch. This ensures that a switch operation is performed. When the car navigation system displays a screen for inputting data, a relatively small resistance is generated for the operation of the rotary switch. This enables smooth input of data.
However, the variable tactile sensation mechanism using the motor may have the following problem. The variable tactile sensation mechanism may have a response delay when the switch knob that has been rotated in one direction is rotated in the opposite direction. More specifically, inertial force is produced when a rotor is being rotated in a motor. When the switch knob is rotated in the opposite direction, the inertial force would interfere with immediate reversing of the rotor rotating direction. This generates a time delay before the motor starts generating rotation in the reverse direction. Thus, a time delay also occurs before a click is generated for the reversed rotation of the switch knob. In this manner, a control delay or a response delay may occur when the switch knob is operated if the variable tactile sensation mechanism uses a motor.
Further, when the motor is connected to the switch knob by a transmission mechanism, such as a gear or a wire, backlash of the gear or expansion of the wire may interfere with direct transmission of the motor drive force to the switch knob when the switch knob is rotated. This may also delay control of the switch knob. Further, the transmission mechanism may rattle the switch knob or lower the rigidity of the switch knob. In addition, the space occupied by the motor and the transmission mechanism may increase the size of the switch.